1. Anti-friction Bearings & Electrical Discharging
Here is an acceleration spectrum recorded on the drive motor of the Penthouse 7 Supply Fan.

2. Sideband peaks occurring at the BPFO defect frequency
Anti-friction Bearings & Electrical Discharging
Sideband peaks occurring at the BPFO defect frequency
High frequency, non-synchronous peaks appear in the upper region of the spectrum. These peaks contain “sideband” peaks that coincide with the fault frequency of the outer race (BPFO) for the outboard bearing.

3. Actual fault frequency is occurring at 3.628xRPM
Anti-friction Bearings & Electrical Discharging
LOOKUP In Bearing File: MVWBRG.DAT
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ID# BEARING TYPE #B/R FTF BSF BPFO BPFI
NSK 6208z
NSK 6208 (MVW)
Actual fault frequency is occurring at 3.628xRPM
The outer race defect (BPFO) lists a defect frequency at orders. The actual faults are occurring at sidebands orders. The frequency is higher because of geometrical changes that have occurred as a result of degradation.

4. Anti-friction Bearings & Electrical Discharging
Over 28 G’s pk to pk acceleration
Impacting with high peak to peak energy
Waveform data indicates signs of severe impacting. Peak to peak energy exceeds 28.0 G’s of acceleration. The waveform data helps determine a sense of severity of the bearing defect.

5. Before bearing replacement After bearing replacement
Anti-friction Bearings & Electrical Discharging
Before bearing replacement
After bearing replacement
A comparison spectrum shows the drive motor condition both before and after bearing replacement. Note the amplitude reduction in the non-synchronous harmonic peaks.

6. A shaft grounding brush was installed on this drive motor!
Anti-friction Bearings & Electrical Discharging
Outer bearing race has indications of “fluting” as a result of electrical discharging.
A shaft grounding brush was installed on this drive motor!